Temperature actuated drop balls and methods and systems for use thereof

ABSTRACT

Disclosed are devices, systems and methods for actuating tools in a well in a reservoir, such as sliding sleeves used to direct fracturing fluid into the reservoir. The sleeves are actuated using drop balls that seat in the tool with sufficient force to cause the sleeve to move. The drop balls are made from a frangible material having a compressed or deformed shape memory alloy component therewithin. After the drop balls have actuated the sleeves in the well, they are exposed to a temperature change from below to above the transition temperature of the shape memory alloy such that the component expands and the frangible material fragments into pieces, such that the pieces allow unobstructed fluid flow in the well. Optionally, a heating element can be used to effect the temperature change.

FIELD

The present disclosure relates generally to the field of fracturing system for a wellbore, and more particularly to balls used to actuate tools such as sleeves used to direct fracturing treatment when fracturing a reservoir.

BACKGROUND

Multiple zone fracturing treatments use “drop balls” to actuate tools in wellbores (also referred to herein as wells). For instance, sleeves that direct fracture treatment fluid in a reservoir during fracturing treatments are actuated by such drop balls, also referred to herein interchangeably as fracturing balls, frac balls and balls. The balls are intended to dissolve over time in the well fluids. Existing balls for this purpose are primarily made from two materials, decomposable polymers and decomposable metals such as a controlled electrolytic metallic (CEM) nanostructured material commercially available under the name IN-Tallic™ from Baker Hughes Inc., a GE Company. Both polymer and metallic frac balls require exposure to water in order to dissolve. In certain situations, it is not possible to guarantee that the balls will have adequate exposure to water to fully dissolve. In this event, undissolved balls can restrict or prevent flow from the well.

There exists a need for drop balls, methods and systems in which the drop balls would be more reliably removed, in either uncemented or cement lined wellbores.

SUMMARY

In general, in one aspect, the disclosure relates to a drop ball for actuating tools in a well in a reservoir. The ball is made from a frangible material having a generally spherical shape and a diameter of from 0.5 to 5 in. The ball includes at least one component containing a compressed or deformed shape memory alloy material located within the frangible material of the ball wherein the shape memory alloy material has a transition temperature of from −60 to 400° F. Upon exposing the ball to a change in temperature from below the transition temperature to above the transition temperature, the at least one component expands or transforms to its original shape thereby causing the frangible material of the ball to fragment into pieces, such that the pieces allow unobstructed fluid flow in the well.

In another aspect, the disclosure can generally relate to a method for actuating tools in a well in a reservoir using the drop ball to fracture the reservoir. The transition temperature is in a range of a static reservoir temperature and an expected cool-down temperature during the fracturing treatment. The temperature of the well remains below the transition temperature during flow of fracturing fluids and exceeds the transition temperature after cessation of flow of fracturing fluids, such that the at least one component of the drop ball expands thereby causing the frangible material of the drop ball to fragment into pieces, such that the pieces allow unobstructed fluid flow in the well.

In yet another aspect, the disclosure can generally relate to a system for actuating tools in a well in a reservoir. The system includes the drop ball, a heating element within the drop ball for effecting the change in temperature of the at least one component of the drop ball from below the transition temperature to above the transition temperature, a battery for powering the heating element, and a programmable chip having a programmed time delay for connecting the battery to the heating element after a predetermined amount of time for controlling the operation of the heating element, such that the component of the drop ball is heated thereby exposing the ball to the change in temperature from below the transition temperature to above the transition temperature, and the at least one component expands or transforms to its original shape thereby causing the frangible material of the ball to fragment into pieces, such that the pieces allow unobstructed fluid flow in the well.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects, features and advantages of the present invention will become better understood with reference to the following description, appended claims and accompanying drawings. The drawings are not considered limiting of the scope of the appended claims. Reference numerals designate like or corresponding, but not necessarily identical, elements. The drawings illustrate only example embodiments. The elements and features shown in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the example embodiments. Additionally, certain dimensions or positionings may be exaggerated to help visually convey such principles.

FIG. 1 shows a simplified view of a wellbore in which a drop ball is applied as known in the prior art.

FIGS. 2A-2C show simplified views of a drop ball according to one embodiment.

FIGS. 3A-3C show simplified views of a drop ball according to another embodiment.

FIGS. 4A-4C show simplified views of a drop ball according to yet another embodiment.

DETAILED DESCRIPTION

In one embodiment, referring to FIG. 1, a wellbore 2 is shown in which embodiments of the present disclosure can be applied. The wellbore 2 (also referred to herein interchangeably as the well) can be an uncemented (i.e., open hole) or a cement lined (i.e., cased hole) wellbore. A wellbore 2 extending into a reservoir 4 can include a liner with open hole packers 3 and sleeves 6. The packers segment the wellbore 2 and the sleeves 6 are used to direct fracturing fluid into each segment of the reservoir 4. Alternatively, the liner with sleeves 6 may be run without packers and cemented into the open hole. The sleeves 6 are used to direct fracturing fluid to first break through the cement around the outside of the sleeve 6 (when cement is present) and into each segment of the reservoir 4.

In one embodiment, a drop ball 10 is provided to actuate the sleeves 6. Each drop ball 10 is configured for dropping into the well to actuate one of the sleeves 6. As is known in the art, drop balls are dropped into the well 2 from the surface at a desired time to begin fracturing the reservoir 4. An example of such a drop ball actuated process is described in U.S. Pat. No. 7,861,774 (Fehr et al.), the contents of which are incorporated herein by reference. Each of the drop balls travels in the well 2 until it strikes a restriction (a seat) 7 in the sleeve 6, at which point the drop ball is said to be “seated” in the sleeve 6. The drop ball 10 seats in the restriction 7 in the sleeve 6 with sufficient applied pressure to cause the sleeve 6 to move, thus actuating the sleeve 6. When the sleeve 6 moves, shear pins (not shown) that initially hold the sleeve 6 in place may be sheared as is known in the art. The applied pressure required to actuate the sleeve 6 can be in a range from 1000 to 10,000 psi. By actuating the sleeve 6, ports 5 within the liner 8 are opened such that fluid can flow through into the reservoir 4.

The drop ball 10 of embodiments disclosed herein advantageously fractures into pieces after being used to actuate the sleeves 6, as will be described hereinafter.

In one embodiment, referring to FIG. 2A, the drop ball 10 can have a generally spherical shape. The drop ball 10 can have a diameter of from 0.5 to 5 in. In one embodiment, the drop ball is capable of withstanding pressures of between 1000 and 15,000 psi, even a pressure of at least 5,000 psi. The drop ball 10 includes a frangible material 11. In one embodiment, the frangible material 11 can be powdered metal, glass, ceramic material, cast material, brittle polymeric material, or a combination thereof. In one embodiment, the frangible material 11 is a material that is soluble in production fluids containing hydrocarbons and/or brine at pressure and temperature conditions in the well 2.

Within the drop ball 10 is at least one component 12 made from (i.e., containing) a shape memory alloy (SMA) material located within the frangible material 11. Generally, shape memory alloys are materials that can be compressed or deformed into a new shape, and then can return to a predetermined, original shape when heated, i.e., expand. When the SMA of the component 12 is relatively cold, or below its transformation temperature, it has a relatively low yield strength and can be deformed quite easily into any new shape, which it will retain.

However, when the material is heated to above its transformation temperature, the material undergoes a change in crystal structure, which causes it to return to its original shape. During its phase transformation, the SMA can generate large force against any encountered resistance or undergo a significant dimension change when unrestricted. The SMA is compressed or deformed with a predetermined amount of force. The recovery force of the SMA can be released most efficiently by heating the SMA to above the transformation temperature to let the component return to its original shape.

The component(s) 12 is a compressed or deformed component, meaning that the component had an original shape and is compressed or deformed to a shape other than the original shape. The component(s) 12 can have a volume within the ball 10 of from 2 to 50% of the volume of the ball. In one embodiment, the component(s) 12 can have a volume within the ball of from 10 to 30% of the volume of the ball 10.

In one embodiment, the component(s) 12 can take the form of multiple pieces of SMA material dispersed within the frangible material 11, as shown in FIG. 3A.

The SMA has a transition temperature in a range of a static reservoir temperature and an cool-down temperature that would be expected during the fracturing treatment. The SMA can have a transition temperature of from −60 to 400° F. In one embodiment, the transition temperature of the SMA is from 150 to 350° F. In one embodiment, the SMA material can be nickel-titanium (NiTi), copper-aluminum-nickel, copper-zinc-aluminum, manganese-copper, iron-manganese-silicon or other shape memory alloys created by alloying zinc, copper, iron or gold, or a combination thereof. In certain exemplary embodiments, the component 12 is constructed of a copper-aluminum nickel (Cu—Al—Ni) shape memory alloy. The Cu—Al—Ni shape memory has a transformation temperature window of about −240 to about 480° F., a maximum recovery strain of about 9 percent, a maximum recovery stress of about 72,500 psi, about 5,000 transformation cycles, a density of about 7.1 grams/cm3, an admissible stress of about 14,500 psi for actuator cycling, an ultimate tensile strength of about 73,000 to about 116,000 psi, and good corrosion resistance. In certain alternative embodiments, the component 12 is constructed of a nickel-titanium-platinum (Ni—Ti—Pt) shape memory alloy. The transformation temperature of the Ni—Ti—Pt shape memory alloy can be as high as 1100° F., depending on how much platinum is added. In certain other embodiments, the component 12 is constructed of a nickel-titanium-palladium (Ni—Ti—Pd) shape memory alloy. The transformation temperature of the Ni—Ti—Pd shape memory alloy can be as high as 1300° F., depending on how much palladium is added.

In one embodiment, the temperature of the well 2 remains below the transition temperature of the SMA during the seating of the drop ball 10 and the resulting flow of fracturing fluids. Subsequently, the temperature of the well exceeds the transition temperature of the SMA after cessation of flow of fracturing fluids, such that the at least one component 12 of the drop ball 10 then expands. In some embodiments, the temperature of the well 2 can be from 100 to 400° F. The expansion of the component 12 causes the frangible material 11 of the drop ball 10 to crack as shown in FIGS. 2B and 3B, and then fragment into pieces 20 as shown in FIGS. 2C and 3C. The pieces 20 do not obstruct the flow of fluid in the well 2. In one embodiment, the pieces 20 are then allowed to fall into a rat hole of the well 2 to allow unobstructed flow of production fluids into the well 2. In one embodiment, the pieces 20 flow out of the well 2 to the surface.

Without wishing to be bound by theory, when the drop ball 10 is exposed to a change in temperature from a starting temperature of below the transition temperature of the SMA to a temperature of above the transition temperature of the SMA, the component 12 expands or transforms from its compressed or deformed shape back to its original shape, thereby causing the frangible material 11 of the ball 10 to fragment into pieces 20. In some embodiments, the expanding component 12 creates cracks that increase surface area exposure of the pieces 20 to production fluids and speed dissolution of the pieces 20.

The component(s) 12 can have any suitable shape, such as, but not limited to, a straight-edged shape, a curved-edged shape, a pellet shape, a wire shape, a plug shape, a bent shape, a coil shape or combinations thereof.

In one embodiment, referring to FIG. 4A, the drop ball 10 further includes a heating element 14 located in the ball 10 for heating the component 12 to effect the change in temperature from below to above the transition temperature of the SMA. In one embodiment, the heating element 14 is controlled using a programmable time delay. The heating element 14 can be a wire wrapped around the SMA. The heating element 14 can be connected to a battery 15 and programmable chip 17 having a programmed time delay for connecting the battery 15 to the heating element 14 after a predetermined amount of time thus controlling the operation of the heating element 14. For example, the predetermined amount of time can be from 1 hour to 300 hours. The programmable chip 17 can be programmed at a surface location. At the programmed time-delay, the programmable chip 17 connects the battery 15 to impart heat into the wire(s) 14 resulting in the SMA 12 transitioning to its expanded shape, thus resulting in cracks and disintegration of the drop ball 10. As above, the expansion of the component 12 causes the frangible material 11 of the drop ball 10 to crack as shown in FIG. 4B, and then fragment into pieces 20 as shown in FIG. 4C.

While the ball 10 can be used to actuate sleeves 6 in a well 2 to direct fracturing treatment into a reservoir 4, as described above, other tools can also be actuated using the ball 10.

In one embodiment, the ball 10 can be used to temporarily plug the liner 8 to allow setting a packer 3 in the well 2. In one embodiment, the ball 10 can be used in pressure testing the liner 8. In one embodiment, the ball 10 can be used for preventing fluid loss to the reservoir 4.

Advantageously, through the use of the disclosed drop balls 10, drop balls can be more reliably removed from wellbores 2 after being used to actuate tools downhole, in either uncemented or cement lined wellbores.

It should be noted that only the components relevant to the disclosure are shown in the figures, and that many other components normally part of a fracturing system for a wellbore are not shown for simplicity.

For the purposes of this specification and appended claims, unless otherwise indicated, all numbers expressing quantities, percentages or proportions, and other numerical values used in the specification and claims are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by the present invention. It is noted that, as used in this specification and the appended claims, the singular forms “a,” “an,” and “the,” include plural references unless expressly and unequivocally limited to one referent.

Unless otherwise specified, the recitation of a genus of elements, materials or other components, from which an individual component or mixture of components can be selected, is intended to include all possible sub-generic combinations of the listed components and mixtures thereof. Also, “comprise,” “include” and its variants, are intended to be non-limiting, such that recitation of items in a list is not to the exclusion of other like items that may also be useful in the materials, compositions, methods and systems of this invention. 

What is claimed is:
 1. A drop ball for actuating tools in a well in a reservoir, comprising: a ball comprising a frangible material having a generally spherical shape and a diameter of from 0.5 to 5 inches for dropping in the well to actuate a tool wherein the drop ball seats in the tool with applied pressure thereby actuating the tool; and at least one component comprising a shape memory alloy material located within the frangible material of the ball wherein the shape memory alloy material has a transition temperature of from −60 to 400° F. and wherein the at least one component is compressed or deformed from an original shape of the at least one component; wherein upon exposing the ball to a change in temperature from below the transition temperature to above the transition temperature, the at least one component expands or transforms to its original shape thereby causing the frangible material of the ball to fragment into pieces, such that the pieces allow unobstructed fluid flow in the well.
 2. The drop ball of claim 1 wherein the at least one component has a volume within the ball of from 2 to 50% of the volume of the ball.
 3. The drop ball of claim 1 wherein the at least one component has a volume within the ball of from 10 to 30% of the volume of the ball.
 4. The drop ball of claim 1 wherein the frangible material is selected from the group consisting of powdered metal, glass, ceramic material, cast material, brittle polymeric material and combinations thereof.
 5. The drop ball of claim 1 wherein the frangible material is soluble in production fluids containing hydrocarbons and/or brine at pressure and temperature conditions in the well.
 6. The drop ball of claim 1 wherein the shape memory alloy material is selected from the group consisting of nickel-titanium (NiTi), copper-aluminum-nickel, copper-zinc-aluminum, manganese-copper, iron-manganese-silicon or other shape memory alloys created by alloying zinc, copper, iron or gold, and combinations thereof.
 7. The drop ball of claim 1 wherein the transition temperature of the shape memory alloy material is from 150 to 350° F.
 8. The drop ball of claim 1 wherein the at least one component has a shape selected from the group consisting of a straight-edged shape, a curved-edged shape, a pellet shape, a wire shape, a plug shape, a bent shape, a coil shape and combinations thereof.
 9. The drop ball of claim 1 wherein the at least one component is in the form of multiple pieces of shape memory alloy material dispersed within the frangible material.
 10. The drop ball of claim 1 further comprising a heating element located in the ball for heating the at least one component to effect the change in temperature from below the transition temperature to above the transition temperature.
 11. The drop ball of claim 10 wherein the heating element is connected to a programmable time delay.
 12. The drop ball of claim 1 wherein the tools are sleeves in a well to direct fracturing fluid into the reservoir.
 13. The drop ball of claim 1 wherein the ball is capable of withstanding a pressure of at least 5,000 psi.
 14. A method for actuating tools in a well in a reservoir, comprising: dropping the drop ball of claim 1 in the well to actuate a tool wherein the ball seats in the tool with applied pressure thereby actuating the tool; wherein the transition temperature is in a range of a static reservoir temperature and an expected cool-down temperature during the fracturing treatment; wherein the temperature of the well remains below the transition temperature during flow of fracturing fluids and exceeds the transition temperature after cessation of flow of fracturing fluids, such that the at least one component of the drop ball expands thereby causing the frangible material of the drop ball to fragment into pieces, such that the pieces allow unobstructed fluid flow in the well.
 15. The method of claim 14 wherein the expanding at least one component creates cracks to increase surface area exposure of the pieces to production fluids and speed dissolution of the pieces.
 16. The method of claim 14 further comprising effecting the change in temperature from below the transition temperature to above the transition temperature using a heating element located in the drop ball for heating the at least one component.
 17. The method of claim 16 wherein the heating element is connected to a battery and programmable chip comprising a programmed time delay for connecting the battery to the heating element after a predetermined amount of time for controlling the operation of the heating element.
 18. The method of claim 14 wherein the tools are sleeves in the well to direct fracturing fluid into the reservoir.
 19. A system for actuating tools in a well in a reservoir, comprising: a. the drop ball of claim 1 for dropping in the well to actuate a tool wherein the drop ball seats in the tool with applied pressure thereby actuating the tool; b. a heating element connected to the drop ball for effecting the change in temperature from below the transition temperature to above the transition temperature; c. a battery for powering the heating element; and d. a programmable chip comprising a programmed time delay for connecting the battery to the heating element after a predetermined amount of time for controlling the operation of the heating element, such that the component of the drop ball is heated thereby exposing the ball to the change in temperature from below the transition temperature to above the transition temperature, and the at least one component expands or transforms to its original shape thereby causing the frangible material of the drop ball to fragment into pieces, such that the pieces allow unobstructed fluid flow in the well.
 20. The system of claim 19 wherein the programmable chip is programmed at a surface location.
 21. The system of claim 19 wherein the predetermined amount of time is from 1 hour to 300 hours.
 22. The system of claim 19 wherein the tools are sleeves in the well to direct fracturing fluid into the reservoir. 